When 4.9 million gallons of crude oil blew out of Deepwater Horizon's well head in the 2010 Gulf of Mexico disaster, emergency responders made the decision to add 2 million gallons of dispersant -- a chemical substance used to prevent settling or clumping -- to the mix.

Emergency Response Questions

The strategy immediately met with a public outcry. Most people were merely following their gut reactions -- how can 2 million more gallons of chemicals poured on top of the growing oil mess possibly be a good idea? Some feared hidden motives: were BP and the associated companies trying to make the problem magically disappear?

We do not want to judge the emergency responders with hindsight. The responders were leveraging an insufficiently tested tool developed to reduce environmental damage from oil globbing and forming large slicks. With oil gushing into the delicate Gulf ecosystem, it was too late to start testing before taking action.

But all who understood the chemistry of what was being attempted looked on with reservations. Even though the chemicals being used appeared to be the lesser of evils, the effects of dispersing oil -- thereby making it more available in the short term to marine animals in the food chain -- represented an unprecedented experiment that was not being pursued in a laboratory but in our precious ocean environment.

Finally, Lab Results on Oil + Dispersants

The results of that grand experiment are still coming in as scientists continue to evaluate the health of the Gulf ecosystem in the wake of the disaster. But lab tests finally done on the oil dispersant deliver clear answers: dispersants FAIL.

The oil-dispersant mixture was 52 times more toxic to the rotifers than oil alone. In addition to the toxicity scientists witnessed in adult rotifers, the oil-dispersant cocktail also inhibited rotifer egg hatching. These results will certainly have scientists looking for declines in baby fish, shrimp, and crab populations caused by starvation.

UAA’s Roberto-Rico Martinez, lead author of the study reports:

Dispersants are preapproved to help clean up oil spills and are widely used during disasters. But we have a poor understanding of their toxicity. Our study indicates the increase in toxicity may have been greatly underestimated following the Macondo well explosion.

Legislation Must Prevent a Repeat

As Martinez notes, Corexit was "preapproved" for the purpose for which it was used. How is it possible that this chemical mixture was approved for exactly this use, but tests such as those done at GIT/UAA were not required as part of the approval process?

Going forward, legislation must clearly require use-related testing be done so that good decisions can be made by people trained in how to minimize the damage when things go wrong. It will not be possible to prevent every disaster, and it may be necessary to take action that is insufficiently tested based on human judgement alone.

But it should never again come to pass that chemicals are approved for a defined purpose without the testing to support that their intended use is better than taking no action at all.